1. Field of the Invention
The present invention relates to a muffler of an industrial engine, and more particularly to improvements in a structure of such type of muffler.
2. Description of the Prior Art
As the above-mentioned type of muffler, the inventor of this invention proposed previously in Japanese Utility Model Application No. 63-127369 (1988), a structure of a muffler of an industrial engine, in which a channel communicating with an exhaust gas outlet is formed integrally on the inside of a muffler main body consisting of a diecast article, an inner lid consisting of a diecast or a sheet metal is joined to the open side of the aforementioned channel, and thereby an exhaust gas passageway serving also as a tail pipe is constructed within the muffler main body.
FIGS. 5 to 7 illustrate the muffler disclosed in the above-referred Japanese Utility Model Application No. 63-127369 (1988), in which on the inside of a muffler main body 100 consisting of an aluminum diecast article having an exhaust gas inlet 100a and an exhaust gas outlet 100b, is formed a U-shaped channel 103 communicating with the exhaust gas outlet 100b by means of a wall 100c constructed integrally with the main body 100, and by joining and fastening, by means of a clamp screw 102, an inner lid 101 consisting of a diecast or a sheet metal on the opening side of the above-mentioned channel 103, an exhaust gas passageway 130 serving also as a tail pipe is constructed within the muffler main body 100, thus as compared to the structure in which a tail pipe is fixed to the exhaust gas outlet 100b of the muffler main body 100, shaping of the tail pipe is facilitated, and also by modifying the shape of the exhaust gas passageway, a path length from the inlet to the outlet can be arbitrarily changed, and tuning with respect to performance (output, noise) is made possible.
However, the above-mentioned structure of a muffler in the prior art involved the following problems. That is, the inlet of the tail pipe is liable to be clogged by carbon because the exhaust gas passageway is abruptly choked and a flow velocity of the exhaust gas changes suddenly there, hence the tail pipe must be cleaned frequently, and also a curved portion of the exhaust gas passageway in the tail pipe is also apt to be clogged by carbon, so that the time necessitating maintenance becomes frequent. In addition, in the above-described muffler in the prior art, since the exhaust gas passageway 130 is formed by joining an inner lid 101 consisting of a diecast or a sheet metal to the open side of the channel 103 formed of a diecast, upon fastening this inner lid 101 by means of a clamp screw 102 there is a possibility that the inner lid 101 may be deviated in position by an amount corresponding to a looseness of a through-hole for the clamp screw, and as a result, there was a fear that the exhaust gas may escape directly through a gap formed by the deviation to the exhaust gas outlet 100b without passing through the exhaust gas passageway 130, and so, the muffler cannot achieve the function of a tail pipe.